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This article mainly explains "detailed introduction of Kubernetes architecture". Interested friends may wish to have a look at it. The method introduced in this paper is simple, fast and practical. Now let the editor to take you to learn "the detailed introduction of Kubernetes architecture"!

Introduction to Borg

Borg is a large-scale cluster management system within Google, which is responsible for the scheduling and management of many core services within Google. The purpose of Borg is to enable users not to worry about resource management, to focus on their core business, and to maximize resource utilization across multiple data centers.

Borg is mainly composed of BorgMaster, Borglet, borgcfg and Scheduler, as shown in the following figure:

BorgMaster is the brain of the entire cluster, which is responsible for maintaining the state of the entire cluster and persisting data to Paxos storage.

Scheduer is responsible for scheduling tasks and dispatching them to specific machines according to the characteristics of the application.

Borglet is responsible for actually running the task (in the container)

Borgcfg is a command-line tool for Borg to interact with Borg systems, usually submitting tasks through a configuration file.

Kubernetes architecture

Kubernetes draws on the design concepts of Borg, such as Pod, Service, Labels and single Pod and single IP. The overall architecture of Kubernetes is very similar to Borg, as shown in the following figure

Kubernetes mainly consists of the following core components:

Etcd saves the state of the entire cluster

Kube-apiserver provides a unique entry for resource operations and provides mechanisms such as authentication, authorization, access control, API registration and discovery.

Kube-controller-manager is responsible for maintaining the status of the cluster, such as fault detection, automatic extension, rolling updates, etc.

Kube-scheduler is responsible for resource scheduling and dispatches Pod to the corresponding machine according to the predetermined scheduling policy.

Kubelet is responsible for maintaining the life cycle of the container and is also responsible for the management of Volume (CVI) and network (CNI).

Container runtime is responsible for image management and the actual operation of Pod and container (CRI). The default container runtime is Docker

Kube-proxy is responsible for providing Service with service discovery and load balancing within cluster.

In addition to the core components, there are some recommended Add-ons:

Kube-dns is responsible for providing DNS services for the entire cluster.

Ingress Controller provides public network access for services.

Heapster provides resource monitoring

Dashboard provides GUI

Federation provides clusters across availability zones

Fluentd-elasticsearch provides cluster log collection, storage and query.

Hierarchical architecture

The design concept and function of Kubernetes is actually a hierarchical architecture similar to Linux, as shown in the following figure

Core layer: the core function of Kubernetes, which provides API to build high-level applications and plug-in application execution environment internally.

Application layer: deployment (stateless applications, stateful applications, batch tasks, cluster applications, etc.) and routing (service discovery, DNS parsing, etc.)

Management: system metrics (such as infrastructure, container and network metrics), automation (such as automatic extension, dynamic Provision, etc.), and policy management (RBAC, Quota, PSP, NetworkPolicy, etc.)

Interface layer: kubectl command line tools, client SDK, and cluster federation

Ecosystem: a large container cluster managing and dispatching ecosystem above the interface layer, which can be divided into two categories

External to Kubernetes: log, monitoring, configuration management, CI, CD, Workflow, FaaS, OTS application, ChatOps, etc.

Kubernetes internal: CRI, CNI, CVI, image repository, Cloud Provider, configuration and management of the cluster itself, etc.

Core component

Core API

ecosystem

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